Lai told reporters in Taipei that he would step down along with his cabinet on Friday.
Lai’s departure was widely expected. It is standard practice in Taiwan for leaders to go when their party loses a major election. The DPP suffered a significant defeat in November to the China-friendly opposition Kuomintang.
It is also customary for the cabinet to step down when the premier resigns.
President Tsai Ing-wen is expected to announce a new premier, Lai said, and ministerial appointments would follow.
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